EFFECT OF X-RADIATION ON CUMINGIA EGGS. 



217 



series. It is evident that the irradiation of the sperm (B series) 

 is not so harmful as a similar irradiation of the egg. 



From a comparison of the number of eggs developing in the 

 different series to that of the control a striking difference is 

 noted. The following table will give by actual count the per- 

 centage of eggs developing in the different lots. We find no 

 eviden'ces in the nuclear structure of parthenogenetic develop- 

 ment. 



TABLE V. 



For a sperm exposure of 3 minutes there is a net increase of 

 almost 6 per cent, of the eggs developing. That is, there is a 

 greater number of fertilizations due to a short exposure of the 

 sperm. A longer exposure shows a decrease in the percentage 

 of fertilizations which is below normal. The C series shows a 

 net decrease of 14 per cent., there being no difference evident 

 between the lots of eggs radiated for the longer or the shorter 

 period. The D series is not, as might be expected, an average 

 of the effect of B and C, but is a further decrease, the increase 

 in the B series not being manifested in the D series. In fact the 

 Di5 eggs show a deviation from normal nearly equal to the sum 

 of the deviations of the 615 eggs plus that of the Ci5 lot. 



It appears, then, if this single set of observations be regarded 

 as typical, that the percentage of Cumingia eggs fertilized is 

 influenced by exposure of the eggs or sperm to X-radiation, and 

 by the amount of exposure which they receive. 



In connection with the effect of irradiation upon the percentage 

 of fertilizations is the question of the effect upon polyspermy, 

 for the same factor which would increase the percentage of 

 fertilization would also tend to increase the number of super- 

 numerary sperm to enter the egg. The results of actual counts 



